Photosynthesis

Photosynthesis

Formula of chlorophyll photosynthesis

The chlorophyll photosynthesis that occurs in nature for all plant beings is made up of a series of chemical reactions and is part of all those anabolic processes, of synthesis, of carbohydrates. In fact, it is a completely opposite process to those inverse processes of catabolism, that is of oxidation.During the process of photosynthesis, through the mediation of the chlorophyll substance, the sunlight allows to convert the six molecules of carbon dioxide in the atmosphere (CO2) and the six water molecules (H2O), in a single glucose molecule (C6H12O6), a sugar that is fundamental and indispensable for the life of every plant. In particular, as a by-product of this chemical reaction, six oxygen molecules are produced, which each plant releases, through the stomata, into the surrounding atmosphere. These stomata are a kind of small holes found on the leaves.The general formula of the photosynthesis process is as follows: 6 carbon dioxide (CO2) + 6 water (H2O) + Light → glucose (C6H12O6) + 6 oxygen (O2) .


Chlorophyll photosynthesis in brief

Thanks to the process of chlorophyll photosynthesis, both green plants and other organisms produce organic substances, generally carbohydrates, starting from the carbon dioxide found in the atmosphere and from metabolic water, always if they are in the presence of sunlight. Chlorophyll photosynthesis is therefore the process that allows the primary production of organic compounds starting from inorganic substances. Perhaps it represents the oldest anabolic process that developed in the first living organisms. In fact, photosynthesis is the only biologically important process that is capable of capturing solar energy and on this depends, essentially the life that exists on Earth today. In addition to the photosynthetic cycle that produces glucose synthesis, plants also carry out an opposite oxidative cycle, also called cellular respiration, of the photosynthetic products used as nourishment for the plants themselves. The balance of oxygen and CO2 towards and from the external environment is however in favor of photosynthesis.


The bright phase of photosynthesis

The so-called light phase is dominated by type a chlorophyll and the molecules absorb light selectively, in the red and blue-violet portions of the spectrum. The captured energy allows the transformation of electrons from atomic orbitals with lower energy to orbitals with higher energy. These are immediately replaced by the splitting of water molecules which is divided into two electrons, two protons and an oxygen thanks to the photolysis process by the "oxygen evolving complex", OEC. The electrons that are released from chlorophyll are fed into the transport chain formed by cytochrome B6f, passing to a lower energy level. The lost one is used to pump protons from the stroma into the thylakoid, causing the so-called proton gradient. The electrons arrive at photosystem I, which, due to the effect of light, loses other electrons which are transferred to the ferredoxin. Thanks to the ATP-synthetase protein on the thylakoid membrane, the H + ions produced by hydrolysis pass to the stroma synthesizing ATP from the free phosphate and ADP groups. For every two electrons lost, an ATP molecule is formed.


The dark phase of chlorophyll photosynthesis

The "carbon fixation" phase, called the "Calvin cycle" involves the transformation of carbon dioxide into organic compounds and the reduction of the ATP compound obtained during the light phase. In the cycle there is an organic compound, ribulose bisphosphate, which is transformed until it returns to its initial state. Its 12 molecules present in the cycle react with water and carbon dioxide transforming thanks to the enzyme ribulose-bisphosphate carboxylase. At the end of the process, 2 molecules of glyceraldehyde 3-phosphate are also created, expelled from the cycle. The Calvin cycle, for activation, needs chemical and support energy through the hydrolysis of 18 ATP in ADP and the oxidation of 12 NADPH in NADP + and in free hydrogen ions H +. The ATP and NADPH consumed in the cycle are taken from the molecules produced in the light phase, and, oxidized, they return to the pool for reduction. Overall, six molecules of carbon dioxide, 6 of water, 18 molecules of ATP and 12 NADPH are consumed in the cycle in order to form 2 glyceraldehyde 3-phosphate, 18 phosphate groups, 18 of ADP, 12 NADP + and 12 protons.



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